Blood flow: Vaginal photoplethysmography

The most widely used method for assessing vaginal blood flow (see Chapters 4.1–4.3 and 5.4–5.6 of this book) is vaginal pho-toplethysmography. The vaginal photoplethysmograph, intro-duced by Palti and Bercovici1 and refined by Sintchak and Geer,2 is made of clear, acrylic plastic and is shaped like a men-strual tampon. Embedded in the device is an incandescent light that projects toward the vaginal wall. Some of the light is reflected back to a photosensitive cell within the body of the probe, while the rest of the light, presumably, is dispersed through the vaginal tissue (for tissue absorption estimates, see Niklas et al.3). Researchers generally assume that more light will return to the photosensitive cell as the amount of blood in the vaginal blood vessels increases. The change is represented as a change in mV from a basal value. In later years, an infrared light-emitting diode was introduced as an alternative to incan